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Stoichiometry Control and Doping of II-VI Semiconductors

National Renewable Energy Laboratory

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Technology Marketing Summary

For II-VI materials and device applications, it is critical to be able to influence both the concentration and lifetime of charge carriers within the material that allow conduction to occur. For example, the inability to increase the carrier concentration in standard polycrystalline CdTe beyond 1015 cm-3 limits solar cell efficiency. Adjusting the stoichiometry of CdTe materials to create material that is more Cd-rich or Te-rich can improve carrier lifetime, but limits the incorporation of dopants that can increase carrier concentration. New technology is needed that enables both a longer carrier lifetime as well as a higher carrier concentration in order for CdTe devices to continue to improve.

Description

Researchers at NREL have invented a method of treating II-VI semiconductors that allows the carrier concentration and carrier lifetime of the material to be influenced while incorporating a dopant. The method involves annealing the material with a compound of overpressured Cd or Te and a dopant  to adjust the stoichiometry of the material. The process can be easily implemented in existing manufacturing environments and can be conducted at high temperatures greater than 600° C, reducing processing time. Devices fabricated using this method have demonstrated increased carrier concentration greater than 1016 cm-3 and a carrier lifetime greater than 25 ns. 

Benefits
  • Increased carrier concentration and lifetime
  • Compatible with existing processes
  • Can be conducted at high temperatures
Applications and Industries
  • CdTe photovoltaics
  • Infrared detectors
  • Focal plane arrays
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Date
Patent 9,419,170
Patent
9,419,170
Controlling the stoichiometry and doping of semiconductor materials
Methods for treating a semiconductor material are provided. According to an aspect of the invention, the method includes annealing the semiconductor material in the presence of a compound that includes a first element and a second element. The first element provides an overpressure to achieve a desired stoichiometry of the semiconductor material, and the second element provides a dopant to the semiconductor material.
National Renewable Energy Laboratory 08/16/2016
Issued
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
NREL ROI 14-01PrototypeAvailable09/07/201709/07/2017

Contact NREL About This Technology

To: Bill Hadley<bill.hadley@nrel.gov>